Other Data (Details) - USD ($) $ in Thousands		3 Months Ended																12 Months Ended
		Dec. 31, 2015	[1]	Sep. 30, 2015	[2]	Jun. 30, 2015	[3]	Mar. 31, 2015	[4]	Dec. 31, 2014	[5]	Sep. 30, 2014	[6]	Jun. 30, 2014	[7]	Mar. 31, 2014	[8]	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
NET INCOME ATTRIBUTABLE TO COMMON STOCKHOLDERS		$ 18,658		$ 27,480		$ 17,916		$ 5,382		$ 18,073		$ 3,991		$ 5,971		$ 3,852		$ 69,436	$ 31,887	$ 6,946
Reconciling items to taxable income:
Depreciation and amortization																		30,457	28,332	26,240
Gain or loss on disposition of depreciable assets																		1,659	(4,940)	(3,656)
Impairments																		687	0	6,222
Straight-line rent																		(8,833)	(12,203)	(6,493)
Receivable allowances																		571	2,074	(716)
Stock-based compensation																		7,518	2,020	5,817
Other																		4,304	1,213	(1,866)
Reconciling items to taxable income, total																		36,363	16,496	25,548
Taxable income	[9]																	105,799	48,383	32,494
Dividends paid																		$ 120,266	$ 116,371	$ 111,571

[1] The increases in net income and amounts per share for the fourth quarter of 2015 are primarily attributable to gains on sales of real estate totaling $9.1 million, partially offset by impairment charges of $0.7 million.

[2] The increases in net income and amounts per share for the third quarter of 2015 are primarily attributable to a $10.6 million gain on the sale of one property previously classified as an asset held for sale.

[3] The increases in net income and amounts per share for the second quarter of 2015 are primarily attributable to a $41.5 million gain on the sale of two properties, partially offset by a $28.0 million loss on extinguishment of the Senior Notes due 2017.

[4] The decreases in net income and amounts per share for the first quarter of 2015 are primarily attributable to impairment charges of $3.3 million

[5] The increases in net income and amounts per share for the fourth quarter of 2014 are primarily attributable to gains on sales of real estate totaling $9.3 million, partially offset by impairment charges of $1.0 million.

[6] The decreases in net income and amounts per share for the third quarter of 2014 are primarily attributable to impairment charges of $4.5 million.

[7] The increases in net income and amounts per share for the second quarter of 2014 are primarily attributable to a $1.9 million cash reimbursement received by the Company for certain operating expenses paid by the Company for years 2006 through 2013.

[8] The decreases in net income and amounts per share for the first quarter of 2014 are primarily attributable to impairment charges of $3.4 million.

[9] Before REIT dividend paid deduction.